Pseudo-icosahedral Cr55Al232-δ as a high-temperature protective material

We report here a course of basic research into the potential suitability of a pseudo-icosahedral Cr aluminide as a material for high-temperature protective coatings. ${\mathrm{Cr}}_{55}{\mathrm{Al}}_{232\ensuremath{-}\ensuremath{\delta}}\phantom{\rule{4pt}{0ex}}\mathrm{[}\ensuremath{\delta}=2.70(6)]$ exhibits high hardness at room temperature as well as low thermal conductivity and excellent oxidation resistance at 973 K, with an oxidation rate comparable to those of softer, denser benchmark materials. The origin of these promising properties can be traced to competing long-range and short-range symmetries within the pseudo-icosahedral crystal structure, suggesting new criteria for future materials research.